The most overtly political sculpture on Trafalgar Square’s fourth plinth since it was given over to contemporary art has been unveiled in central London.

Gift Horse, by the German-American artist Hans Haacke, features an LED bow showing a ticker of the latest London stock prices tied round the bronze skeleton of a horse. It is being seen as a symbol of the ravages of the market.

London’s pro-City mayor, Boris Johnson, made light of the anti-capitalist work at Thursday’s unveiling, two months before the general election.

“There will be those who say that this undeniably underfed beast … is a symbol of the excessive pursuit of austerity and the [chancellor] George-Osborne-diet approach to life. But I say absolutely not,” Johnson said.

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The mayor added his own tongue-in-cheek interpretation of “this emaciated quadruped” after some had expressed surprise that he had not vetoed it before it was given an 18-month stint on the plinth. He said: “In those fabulous tubular structures you will see symbolised the vital infrastructure – the tube that must run beneath the surface of any great and beautiful city. The tubular structures that have received such fantastic investment thanks to our chancellor… and indeed playing a part in the greatest economic recovery this city has ever seen, and the driving force of the UK and indeed [the] European economy.”

The mayor turned to Haacke, beside him, to say: “I hope you share my artistic interpretation,” sparking laughter from an audience that included many senior figures from the art world.

The fourth plinth commissioning group is well aware of the political nature of the work. The artist Grayson Perry, a member of the group, tweeted: “I am very pleased that Hans Haacke’s Gift Horse will be on the fourth plinth in the runup to the election.”

Ekow Eshun, the culture commentator and former director of the ICA, who chaired the group, said Gift Horse “was a very contemporary comment on the connections between power, money and history which go to heart of what London is as a city”.

Grayson Perry (@Alan_Measles)

I am very pleased that Hans Haacke's Gift Horse will be on the Fourth Plinth in the run up to the election. Unveiling on Thursday morning

After the ceremony, Haacke said the work, which was partly based on engravings by the 18th century artist George Stubbs, was a comment on the supposed “invisible hand” benefits of the market described by Stubb’s contemporary Adam Smith. Smith believed that people pursuing their own interests could benefit society more than if they directly tried to help it.

“That is a metaphor that is being used a great deal these days, particularly by people who would like to see the financial industry unregulated,” Haacke told the Guardian. “So it’s an invitation to think about whether the invisible hand of the market does promote general welfare or whether there’s a misunderstanding, or whether it is totally wrong.”

He said the mayor’s interpretation was “odd” but that he did not want to dictate how people saw the work.

Asked whether his piece was a criticism of the power of money, Haacke said: “The title is Gift Horse and that implies that something is off… The little I know about British politics is that austerity is the official programme, so I heard him [Johnson] question that I was surprised.”

Pressed on whether the work was an attack on austerity, he said: “I’d like to leave that open [to interpretation]. It is an invitation to make connections, but I don’t want to give directions about which connections are to be made.”

The artist, who was born in Cologne, has a long record of deliberately provocative work. A piece for the Museum of Modern Art in 1970 attacked donors to the museum for their backing of the Vietnam war. And a work about slum landords was banned from the Guggenheim for being too political.

The Tate director, Sir Nicholas Serota, defended the choice for the fourth plinth, saying Haacke was “a very fine artist who has consistently exposed those things that need to be exposed in the world”.

The fourth plinth had originally been intended to display a statue of William IV on a horse, but was never completed owing to lack of funds.